A RADIAL AIRCRAFT TIRE REINFORCED WITH TWISTED

MONOFILAMENTS Field of the Invention

The present invention relates to a radial aircraft tire which moves at high speed, carries heavy loads and which is inflated at relatively high pressures.

Background of the Invention

Aircraft tires are subjected to high centrifugal forces and heavy loads on takeoff, and high sudden impact forces during landing. In order to meet the required performance, nylon multifilament cord fabric with high epdm (end per decimeter) is generally used in reinforcement of large number of carcass layers and belt layers in aircraft tires.

In the prior art, multifilament nylon cord is preferred in reinforcement for aircraft tires due to its superior fatigue resistance. At the same time such cords have high level of toughness (breaking energy) and resistance against foreign object damage. That is why nylon multifilament cords are widely used in aircraft tires as carcass, belt and protection layer. However one problem with these reinforcements as belt and protection layer is their poor cut resistance against sharp objects. The second problem related with these conventional multifilament nylon cords is loss of their breaking strength during flexing under high tensions. The fretting between the interface filaments having mutually cross angles during flexing under tension gives rise to filament breaks and loss of breaking strength in carcass cords at flex zones. Under tension, the interface filaments of the mutual cord plies have contact points applying sawing effect on each other. The materials having higher cut resistance such as aramide ( evlar, Twaron etc.) are not suitable for being used as reinforcement in aircraft tires due to their poor breaking energies (toughness). When used with very high twist levels in order to increase their breaking energy, this results in drastic loss in breaking strength.

Summary of the Invention

The objective of the present invention is to provide a radial aircraft tire reinforced with twisted monofilaments used in aircrafts moving at high speeds with heavy loads.

Another objective of the present invention is to provide a radial aircraft tire the durability of which is improved by increasing its resistance against impacts.

Detailed Description of the Invention

"A radial aircraft tire reinforced with twisted monofilaments" developed to fulfill the objective of the present invention is illustrated in the accompanying figures wherein,

Figure 1 is the cross-sectional view of the structure of the inventive radial aircraft tire.

Figure 2 2x1 is the view of the cord made of two monofilaments.

Figure 3 3x 1 is the view of the cord made of three monofilaments.

Figure 4 is the view of the cord samples with monofilaments (cross-sections)

Figure 5 is the view of the hybrid cord samples with different monofilaments (cross-sections)

The components shown in the figures are each given reference numbers as follows:

1. Reinforced radial aircraft tire

2. Radial carcass

3. Tread

4. Protective layer

5. Belt layers

6. Twisted cords 7. Crown reinforcement

H. High modulus monofilament

L. Low modulus monofilament The inventive radial aircraft tire reinforced with twisted monofilaments (1 ), which is suitable to be used in a vehicle moving at high speeds with heavy loads, has at least one radial carcass (2); tread (3); at least one protective layer (4); at least one belt layer (5); a crown reinforcement(belt package including protective layer) (7) comprising layers or strips reinforced by cords (6) oriented relative to the equatorial plane of the tire at an angle of between 0° and 35° and wherein at least one layer or layer made of strips has cords (6) made of twisted polymeric monofilaments (Figure 1 ).

In the preferred embodiment of the invention, the cords (6) made of twisted monofilaments can also be used in carcass, belt and/or protection layer in the aircraft tire. These monofilaments which are used are defined as "the polymer fibers having diameter equal or higher than 0.050mm". It is known that the filament diameters of cords currently used as tire reinforcement vary between 0.010 and 0.030 mm.

In the preferred embodiment of the invention, monofilaments are manufactured from nylon 6.6.

In another embodiment of the invention, monofilaments are manufactured from nylon 6 (polycaprolactam).

In another embodiment of the invention, monofilaments are manufactured from PET (polyethylene terephthalate). In the preferred embodiment of the invention, the twisted cords (6) are in hybrid cord structure comprised of different monofilaments with high modulus (H) and low modulus (L). The diameters of the monofilaments are between 0.050mm and 1.00mm. The cords obtained with these monofilaments comprise minimum 2 and maximum 21 monofilaments. The twist levels of the cords made of monofilaments are between 20tpm and 300 tpm (turns per meter). The twist directions can be Z or S, or combination of these.

In the preferred embodiment of the invention, the strip width of the belt reinforcements is between 5mm and 30mm.

In the preferred embodiment of the invention, the cord density of the monofilament cord fabric or the monofilament cord strip is minimum 25 and maximum 150 epdm (ends per decimeter).

In the invention, the material used as monofilament is preferably nylon 6.6. However, PET (polyethylene terephthalate) can also be used. Hybrid cords comprising nylon 6.6 and PET monofilaments can also be used as reinforcements in carcass (2), belt (5) and protective (4) layers.

The construction of cords (6) made of filaments are similar to the construction of steel cords well known in tire technology. Some examples of cord constructions can be given as follows: 2x1 , 3x1 , 4x1 , 5x1 , 6x1 , 7xl(or 1 +6), 8x1 , 9x1 , 10x1 , l lxl , 12x1 , 1+2, 1+3, 1+4, 1+5, 1+6, 1+7, 2+2, 2+3, 2+4, 2+5, 3+1 , 3+2, 3+3, 3+4, 3+9 etc. The twist directions can be Z or S, or combination of these.

The cord twist can change from 20 to 300 tpm (turns per meter), and the diameters of the monofilaments can change from 0.050 to 1.0mm. Carcass (2) and belt (5) have at least two layers. All or some of the belt layers (5) can be spirally wound in belt package as strip (0° to 5° angle with equatorial plane). The cords (6) made of monofilaments can be used as fabric or strip in their applications. In case of strips, strip width can change from 5mm to 30mm. The cord densities (epdm: ends per decimeter) in fabrics and strips can change from 25 to 150 cord/dm.